Basil suffers from concussion when an ornamental moose head falls on him. When he gets home from hospital, still suffering from the effects of his accident, he cannot help but insult his latest guests, a group of Germans.
Even though The Germans features some of the most frequently quoted Fawlty Towers dialogue ("Don't mention the war!"), I do feel that it is a rather uneven episode: the first act features some great gags involving the stuffed moose head (love the Major's conversation with the moose!), but it also suffers from a drawn out and not very funny scene about a fire drill.
Thankfully, the second act—the part with the Germans—is all-out hilarious, with John Cleese giving us some of his greatest comedy ever, making numerous references to the war ("So that's two egg mayonnaise, a prawn Goebbels, a Herman Goering and four Colditz salads"), and performing a brilliantly funny walk as he does his Hitler impersonation.